Georgetown University is conducting a natural history study of chronic non-A, non-B (NANB) hepatitis. The overall objective of the five-year retrospective epidemiologic study is to determine the clinical, biochemical, and histological information on patients who developed posttransfusion hepatitis (PTH) and compare it with transfusion recipients who did not develop PTH. Specifically the contractor must: 1) identify patients who developed NANB PTH in previously completed prospective studies, as well as a group of controls from the same studies; 2) locate the medical records of all individuals identified and invite the survivors to participate. This would include an initial re-evaluation (history, physical examination, and biochemical tests); and 3) follow patients from both groups at six-month intervals for three years. Subjects defined as having had acute NANB PTH in previous studies (specifically, the Transfusion-Trans-mitted Virus Study, and the Veterans Administration Cooperative Study of Posttransfusion Hepatitis) must be identified and the supporting data confirming the diagnosis and form of hepatitis (icteric or anicteric) must be made available.